Consumer demand for electric power typically varies, often considerably, during the course of a single day. Moreover, each individual consumer's demand for electric power generally is highly correlated with other consumers connected to the same power grid. For example, many consumers are likely at or near the same time to increase their energy consumption during the morning hours when consumers are first waking up and want to have plenty of hot water for bathing. Similarly, the demand for electric power drawn from the power grid is likely to increase jointly during summer afternoon hours when numerous consumers are running their air conditioners. Peak demand, of course, affects network capacity and for an electrical energy provider to purchase electrical energy from other suppliers connected to the same electric power grid. Reducing peak demand can avoid building generating capacity for a small peak timer period, say 100 hours during the summer.
In order to address the situation, some electrical energy providers have adopted multi-tier pricing. During certain periods of the day corresponding to high-demand periods, consumers are charged a higher price, and correspondingly, during periods of low demand consumers are charged a reduced price for electric power. The pricing scheme is intended to shift consumer demand so as to reduce electric power consumption during periods that are otherwise high-demand periods.
To take advantage of the pricing scheme, the electrical transmission network can include a mechanism for conveying over power lines (not limited, however, to a power line conveyance, but including for examply an FM radio sub-carrier) a so-called triggering pulse, which signals the beginning of a reduced-rate period. The pulse can be used for specific equipment configured to recognize the pulse, such as a water heater that is enabled in response to the pulse.
An inherent problem with current implementations of such schemes, however, is that the result can be the opposite of that intended. For example, if the triggering pulse is transmitted by an electrical energy provider to a large population of its subscribers, power consumption can spike as various electricity-consuming appliances simultaneously turn-on or are enabled to thermostatically turn on in response to the triggering pulse.